This invention relates to a process for the preparation of fluoromethyl aromatic compounds, and, in particular, to a process for the catalyzed vapor phase replacement of halogen atoms of halomethyl aromatic compounds with fluorine atoms.
Various fluorination processes are known wherein fluorine replaces substituents of organic compounds, such as halogen atoms. Known processes of this type include both vapor phase fluorination reactions and liquid phase fluorination reactions. Typically, such processes involve the reaction of an organic halide with a fluorinating agent, such as hydrogen fluoride, sometimes in the presence of a catalyst, at atmospheric or super-atmospheric pressures. However, many of the known processes, while suitable for laboratory investigations and experiments, or small scale preparations, are unsuitable for larger scale commercial use for various reasons, such as the low purity of product obtained as well as the high cost of equipment employed. In addition, many of the known commercial fluorination processes employ catalysts which, although useful in obtaining an increase in efficiency of the fluorination reaction, present difficulties such as the frequent need for replacement due to loss, deactivation or physical deterioration of the catalyst. For example, one of the common difficulties encountered in vapor phase fluorination reactions results from the highly exothermic nature of such reactions. The heat evolved frequently results in a temperature rise sufficient to cause thermal decomposition of some of the organic materials present with a resultant carbonization of the catalyst. In other instances, materials that provide good catalytic activity for a given reaction under laboratory conditions are too costly or lack the physical stability desirable for use as a catalyst under the rigorous requirements of a continuous commercial process.
A wide variety of fluorination catalysts are known and have been used for various fluorination processes. However, the efficacy of a particular catalyst is highly specific and may depend on the nature of the reactants, that is, the specific compound to be fluorinated and the particular fluorinating agent employed as well as the condition of the fluorination reaction, such as temperature, pressure, and physical phase of reactants.
It is an object of this invention to provide an improved process for the catalyzed vapor phase fluorination of chloromethyl aromatic compounds. It is a further object to provide such process utilizing an improved catalyst therefore that is highly effective, relatively low in cost, and stable under conditions of vapor phase fluorination of chloromethyl aromatic compounds. It is a still further object to provide an improved vapor phase process for the production of trifluoromethyl aromatic compounds.